Fourteen months ago, as ordinary Syrians were just beginning to gather in large numbers to call for their leaders to quit power, a cherub-faced 13-year-old named Hamza Ali al-Khateeb was taken into custody after he’d been caught scrawling an antigovernment slogan on a wall at a protest in the town of Jiza. A month later, when Hamza’s body was returned to his parents, it bore signs of the most hideous torture. His face had been beaten purple, his jaw and kneecaps pulverized, his body stabbed and torched. His penis had been chopped off.

There was a time, and not so long ago, when a Syrian dictator could plausibly assume that such a demonstration of official sadism would silence any popular murmurings for a more democratic form of governance. Brutality always worked before. But by April 2011, the Middle East had changed — Syrians had changed, even if the regime of Bashar al-Assad had not. The mutilation of young Hamza did not crush the Syrians; it enraged and catalyzed them. The result, little more than a year later, is an epic struggle that horrifies and inspires. It’s hard to imagine that the dictator and his confederates can hang on, but still they do.

In “The Syrian Rebellion,” the Middle East scholar Fouad Ajami weaves the threads of Syria’s past with the events of the previous year to give us a portrait of the country as it hurtles toward its moment of decisive transformation. This is no small feat: Syria is a country of enormous ethnic and religious complexity, and the story is moving very fast. “The Syrian Rebellion” is an elegant and edifying book, written on the fly, by an observer who retains an almost loving intimacy with his subject. But it is underlain by a sobering subtext: Ajami suggests that the dynamics of Syria’s politics and history are leading inexorably toward a catastrophe, or at least no quick and happy end. If he’s right, we have probably not yet seen the worst.

Syria is another of the improbable constructions that arose from the ruins of the Ottoman Empire after World War I. The new country was a grab bag of ethnicities and religions, conjured up by colonial mapmakers with little regard for either. In Syria, the dominant group is not the Sunni Arabs, who make up the overwhelming majority; nor even the Christians, a significant minority; but the Alawites, a heterodox Shiite sect that constitutes 12 percent of the population. A largely rural people at the time of Syria’s birth, the Alawites came to dominate first the military and then the country itself. Their ascent was aided by the French, who ruled until the 1940s, and who, in the way of the colonial master, maintained a policy of favoring minorities at the expense of the Sunnis. Hafez al-Assad, a steely-eyed air force officer, secured his hold on power in the 1970s, using the secular-minded Baath Party as his vehicle (its sister party, eventually led by Saddam Hussein, lay across the border in Iraq). When Hafez died, in 2000, he bequeathed power to his son, the London-educated Bashar, age 34.

The old man, as Ajami shows, pursued his designs with a brutal logic, setting up a ruling class of Alawites, some Christians and a select number of Sunni businessmen, stifling dissent, stifling the Sunni majority’s yearnings for a freer expression of their faith, offering instead the slogans of Pan-Arabism and permanent war with the Jews. “Let them eat anti-Zionism,” is how Ajami describes it. There was little flexibility in the regime, little color, no air. The defining moment came in 1982, when an uprising broke out in the predominantly Sunni city of Hama, led by the Muslim Brotherhood. Assad crushed the revolt with savage finality, leveling entire blocks and killing as many as 30,000 of his countrymen. For 29 years, Hama stayed quiet.

Then, in 2000, came Bashar, the heir with the British-Sunni wife, the not-quite-favored son (the chosen, Basel, died in a car accident), the ophthalmologist with no chin. Ajami makes it clear that Bashar was not his father’s equal — neither in competence nor in temperament — and that an already despotic regime transformed into a decadent enterprise without the self-discipline that had once checked its worst abuses. “Pity the Syrians,” Ajami writes. “They had been raised on the legend that their country was the ‘beating heart of Arabism.’ They woke up amidst the debris, and this squalid kleptocracy was what they had gotten in the bargain.” I can personally attest to the decadence: In the summer of 2003, I spent many sleepless nights at the Sheraton Hotel in Damascus, then the city’s main social spot, kept awake by the boisterous up-till-dawn partying of the Syrian elite. Creepy indeed, in a police state. There were widespread doubts about Bashar, whether he had the necessary character to rule Syria, whether he had the guts.

Well, now we know. Bashar al-Assad seems every bit as willing as his father to destroy the country in order to save himself. In December, after Bashar’s military had killed its 5,000th fellow Syrian, the United Nations announced that it was no longer able to count the victims. (How many are there now?) Not long after, Bashar gave a speech ruthless enough to put a pit in your stomach. “Those states that counsel us to reform have no knowledge of democracy whatsoever,” he said. On the walls of the Sunni mosques, the ones he hasn’t ordered to be shelled, the government’s thugs scrawl: “Your God is Bashar.” In Hama, which came alive again after so many years, crowds carry placards: “Like Father, Like Son.”

Where does it end? Ajami leaves no doubt that the Assad family project, especially Bashar’s, was an essentially sectarian one. In this respect, Syria resembles its neighbors, Lebanon and Iraq, the former once ruled by a Christian minority, the latter by the minority Sunni Arabs. Remember what happened in those places? In Syria, the Alawites stand as a sort of palace guard, with everything to lose. (So far, very few have defected to the rebels.) It is not hard to imagine a fight to the death.

That dark prospect surely explains the reluctance of the Obama administration to try to stop Bashar’s killing machine, even as the Syrian rebels beg for our help. It’s too easy to envision an Iraqi-style blood bath after Bashar’s demise. Ajami is frustrated by Obama’s passivity, and indeed, as the killing goes on, it is getting harder for all of us to avert our eyes. Why is Syria different from Libya, where Obama and NATO, at very low cost, stopped an almost certain humanitarian disaster? Why is it different from Yugoslavia?

We may find out soon, whether we like it or not. As Ajami says, Bashar’s regime is in a race against itself. It must crush the rebellion before it ruins the economy. Even the Russians and the Chinese, faithful fellow oppressors, are embarrassed by the butchery. At some point, it seems likely, the regime will crack. It is then, and only then, that we will discover the true Syria, whether it was just an improbable creation set on the banks of the Euphrates, or a real nation after all.

Dexter Filkins is a staff writer at The New Yorker. He is the author of “The Forever War.”